1. Field of the Invention
The present invention relates to a method of gear or shaping by a gear-type gear cutter as one of the shaping processes by generating for producing profiles on workpieces, especially on cylindrical gears. The workpiece and a shaping tool are rotated continuously according to a fixed preset transmission ratio. The tool additionally carries out an oscillating movement in the direction of its axis of rotation and thereby generates small cuts on the workpiece during at least two shaping turns or rotations.
The present invention also relates to an apparatus for performing such a method, and includes a rotatably driven shaping tool which carries out a stroke movement in the direction of its axis of rotation, and also includes a rotatably driven clamping device for the workpiece, whereby the rotary motions of the tool and of the clamping device occur continuously according to a fixed preset transmission ratio.
The tool and the workpiece carry out a rotary motion during shaping to generate a profile, for example for the manufacture of cylindrical gears; the axes of rotation of the workpiece and of the impact spindle are arranged parallel to each other when producing cylindrical workpieces. Superimposed on the rotation of the tool is a linear stroke movement in the direction of the axis of the tool for chip removal.
The workpiece flank is approximated during gear shaping by generating by making individual small cuts, whereby the shaping tool, for the purpose of chip removal, carries out an oscillating stroke movement in the direction of its axis of rotation. Thus a profile with peaks and valleys, which diverges more or less from the ideal profile, results on the workpiece flank as a result of the small cuts.
2. Description of the Prior Art
The approximation of the workpiece flank to the ideal profile by means of individual small cuts becomes better the smaller the generating feed, i.e. the path about which the workpiece is rotated between the formation of two small cuts carried out directly one after the other and accordingly the slower the workpiece rotates and the larger the number of tool strokes per unit of time. Limits are set for the number of strokes per unit of time for dynamic reasons, for instance oscillations of the machine, tool, workpiece and/or clamping device, and possibly also for technological reaons, for instance too great a roughness of the workpiece flank or too great a tool wear. A good approximation of a shaped tooth flank to the ideal flank accordingly necessitates a relatively low workpiece speed. However, in certain instances the machining must occur at a relatively high workpiece speed and accordingly, with a fixed number of strokes also at a high generating feed. Thus a smaller tool wear is obtained in certain situations during shaping by generating at high generating feed than is obtained during conventional shaping by generating. A gear cutting machine also exists upon which simultaneously two gear systems can be produced by chip removal, the two gear systems, particularly cylindrical gear systems, being formed on a common base body. The machining of the one tooth or gear system occurs by hobbing, and that of the other tooth system occurs by gear shaping by generating. In such a case, the workpiece speed, for economical reasons, is preset via the hobbing process; the workpiece speed, in particular when using multiple and possibly coated hobbers, is considerably higher than with conventional shaping by generating. While frequently during conventional shaping by generating, a single workpiece rotation is sufficient for the finishing operation, i.e. for actual profile shaping, because of the small generating feed, several workpiece rotations are necessary for this profile shaping at high generating feed.
In all of these cases, as a consequence of the relatively high generating feed, there result correspondingly large profile shape deviations which under ideal conditions, i.e. when machine and tool are geometrically, statically and dynamically accurate, increase approximately quadratically with increasing generating feed.
It is an object of the present invention to provide a method and an apparatus such that, with a preset number "i" of the shaping rotations, and with preset design data of the tool and workpiece, the procedural profile shape deviations become minimal, and such that the optimum cutting speed for the respective machining case is practically unaffected, so that a minimal profile shape deviation is obtained.
This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in connection with the accompanying drawings.